Rechargeable Power Source from Rechargeable Cells

[Voltz]

This is something I want to base a lot of my future projects on so I need to know this one, first I need a simple charger for a regular 1.2V Ni-MH Battery, (AA or D Cell), but I need it so that the charger can be disconnected from a jack and then the Battery begins doing the work... i.e. LED array, when the Battery is charging power comes from the Mains, when the Battery is not charging power comes from the Battery

So basically I need one circuit for charging the Battery (I've seen lots online but they look too obscenely complicated to be for a simple Ni-MH D/AA cell battery)
And one circuit for switching between mains and battery power

 

[Hero999]

I don't understand, why not simply use a mains powered battery charger to charger to charge a battery?

 

[erendesh]

I do not think this is so complicated. A simple diode like BAT54C can do your job, provided Mains output ( which should be regulated and stepped down) is greater than battery output voltage.

 

[Dragon Tamer]

Some people may sat that I'm obsessed with this part, but try a MAX712. It's not too complicated for your function, and can event be left attached to your battery if needed. It can be programed to however many cells you have and can even power the load if the battery is removed. All you need to do is to calculate what values you need to use to get it to sense properly.

 

[Voltz]

Basically I want a project box with a jack socket which can be connected through a power supply ( I don't want to have to take out the batteries to charge them) and I also want it so that when the batteries are charging all power comes from the mains

 

[Voltz]

BUMP, I just need to know what voltage you need to charge a 1.2V Ni-MH Battery

 

[cowana]

It's current, not voltage.

Say the battery capacity is C.

You can charge at:
2C for 30 minutes (with some batteries)
1C for 1 hour (with some batteries)
0.5C for 2 hours
0.1C for 14 hours
0.01C indefinitly
etc

Andrew

 

[Voltz]

fine okay then, What current in would you recommend for charging a 1.2V NiMH Battery...

 

[bychon]

It depends on the amp-hours in your batteries. Read the label on the batteries.

 

[transistor495]

This is something I want to base a lot of my future projects on so I need to know this one, first I need a simple charger for a regular 1.2V Ni-MH Battery, (AA or D Cell), but I need it so that the charger can be disconnected from a jack and then the Battery begins doing the work... i.e. LED array, when the Battery is charging power comes from the Mains, when the Battery is not charging power comes from the Battery

So basically I need one circuit for charging the Battery (I've seen lots online but they look too obscenely complicated to be for a simple Ni-MH D/AA cell battery)
And one circuit for switching between mains and battery power

I don't understand much from this post, especially where you've specified the 'LED array'?

 

[audioguru]

Go to www.energizer.com "Technical Details" to see detailed datasheets and Applications Manuals for every battery they sell.
Their Ni-MH cells are fully charged at 1.4V each when charged at a low current and are 1.5V to 1.6V when charged at a high current.
They get hot and have a very high internal pressure when overcharged and might "vent" gasses and chemicals.
Their trickle charge current is recommended to be low at only 1/40C.

My Energizer charger for their 2500mAh Ni-MH AA cells charges them at about 500mA for 6 hours. It is simply a stupid timer. It severely over-charges cells that already have some charge. A good charger circuit will detect when the cells are fully charged then shut off or switch to a low trickle charge.

My sound Level indicator project (20 bright LEDs in a VU meter) is usually powered from a 8.5V/350mA wall-wart AC-DC adapter which also continuously trickle charges its 8.4V Ni-MH battery (7 cells).
My charger circuit is the voltage limit of the wall-wart (about 9.8V) and a current-limiting resistor. It has worked perfectly for years. The battery is slightly warm when trickle-charging. There is no switch, the battery powers the circuit when the mains electricity is not present.

 

[Voltz]

Go to www.energizer.com "Technical Details" to see detailed datasheets and Applications Manuals for every battery they sell.
Their Ni-MH cells are fully charged at 1.4V each when charged at a low current and are 1.5V to 1.6V when charged at a high current.
They get hot and have a very high internal pressure when overcharged and might "vent" gasses and chemicals.
Their trickle charge current is recommended to be low at only 1/40C.

My Energizer charger for their 2500mAh Ni-MH AA cells charges them at about 500mA for 6 hours. It is simply a stupid timer. It severely over-charges cells that already have some charge. A good charger circuit will detect when the cells are fully charged then shut off or switch to a low trickle charge.

My sound Level indicator project (20 bright LEDs in a VU meter) is usually powered from a 8.5V/350mA wall-wart AC-DC adapter which also continuously trickle charges its 8.4V Ni-MH battery (7 cells).
My charger circuit is the voltage limit of the wall-wart (about 9.8V) and a current-limiting resistor. It has worked perfectly for years. The battery is slightly warm when trickle-charging. There is no switch, the battery powers the circuit when the mains electricity is not present.

That last paragraph sounds good, schematic?

 

[audioguru]

That last paragraph sounds good, schematic?

My Sound Level indicator project uses an LM3915 IC for a 30dB range plus I added an automatic gain control for an additional 20dB. It shows a pin dropped on the floor of the next room and also shows loud music or screaming.